What is your riding level?
What are you looking for in a horse?
Here's my 2 cents. From the pictures she seems to track up fine and move like a good TB can. However she really looks to be leaning into the bit in some of those pictures, like she's trying to evade is by tucking her head to her chest, leaning down, and running off. Now you can't tell that from the picture, but in my experience that's probably what's going on. The fact that the lady was yelling Short! Short! in the jumping video keys us in to the fact that she probably rushes fences or gets strung out and long to them. None of these problems are something a capable rider couldn't fix.
The only other thing that makes me suspicious, in my area a horse with "Training and Prelim potential" would not be for sale for $2,000. She's young, I'd think that they'd charge a little more, wouldn't you? That makes me think that there may be some sort of medical problem hiding here. There may not, and they may just need a fast sale, but if you become serious about buying this horse, please get a vet check! The initial purchase cost will not amount to anything if you end up having to pay 10 times that in vet bills.
All of that said, I like this horse. From what I can tell she seems like an excellent prospect for a capable rider. I've always had a soft spot for TB's and she seems like she'll make an excellent Eventer.
Good Luck in you horse shopping!